1. Field of the Invention
The present invention relates generally to sheet-fed printing press, or more precisely, to apparatus for adjusting gripper-base height of sheet transfer cylinder in compliance with sheet thickness.
2. Description of the Prior Art
In a sheet feeder unit or printing units of sheet-fed printing press, there are many sorts of sheet transfer cylinders such as intermediate cylinder or perfecting cylinder and gripper-base must be provided at the circumference of cylinders for gripping and transferring sheets with grippers which are driven harmoniously.
In accordance with the change of sheet thickness to be printed, height of gripper-base which is a receiver of grippers must be adjusted and, if not adequately adjusted, fatal printing impediments such as register error or fan-out will inevitably be caused.
Apparatus for adjusting gripper-base height is disclosed in Japanese patent No. 2779136 in which an adjustment shaft is moved in a radial direction of cylinder by a motor disposed at the end of cylinder axis by way of clutch means in order to shift a slide wedge which is parallel to the cylinder axis. But, as such clutch means is interposed, it is difficult to recognize level position of height adjustment by the technique. In addition, such slide wedge narrowly allows very strict manufacturing precision, and on top of that, fine height adjustment is difficult.
In Japanese published patent application No. 29586/1996, plurality of gripper-bases provided at the circumference of the cylinder are adjusted all together by adjustment discs on both sides of the cylinder. But, start point of adjustment is restricted only from both sides of cylinders by the technique, therefore, scattering of adjustment is caused due to bending of members and the technique is substantially a manual operation.